with yb,s flying for 2 hours plus then stopped given a jag put in basket for 7 days then tablet . it could very well be just cramp i would wait a bit before giving any more treatment. if just cramp the stress in birds will also be very high as birds won,t know whats hit them. to learn yb,s how to cope in basket put gully pots in nest boxes .then yb,s from nest boxs straight in to baskets for week. thrush is posibil with yb,s getting a jag then an antibiotic with system fighting their jag. then again with it being flagyl 400 should take care of thrush.i would put a dose of multi vits in water